Lactic acid oligomers are commonly utilised as intermediates in the synthesis of high molecular weight poly(lactic acid) products. There is however also a growing interest for lactic acid oligomers as such. They receive special attention in the field of medical applications for instance for the production of implantable medical devices and scaffolds. Because of their intrinsic properties and their biological-based character they can be also used in added-value domains such as                a substitute for waxes, oils and oligomers currently used in the pharmaceutical formulation domain,        macromers (building blocks) for the polymerisation or copolymerisation of new and existing polymers,        new products in such sectors as binding agents, plasticisers, adhesives, lubricants, inks, nucleating agents, compatibiliser, etc. where physical and chemical properties are key parameters to the performance of the material and are achieved by tailoring the material at molecular scale. Lactic acid oligomers are usually composed of a few and limited number of lactic acid units and can be obtained by polycondensation methods: the hydroxyl and carboxylic acid groups of lactic acid react together and removal of the water formed during this condensation reaction results in the formation of longer polymeric chains of lactic acid.        
The main drawback of this process is the occurrence of numerous competitive reactions resulting in significant amounts of structurally unclear components. Transesterification reactions, both inter and intramolecular, can occur during the polycondensation. Impurities such as carboxylic acids (e.g. formic acid, acetic acid, propionic acid etc. . . . ) or alcohols (e.g. methanol, ethanol, propanol etc. . . . ) in the monomer (lactic acid) can act as chain terminators. Therefore, polymers of different sizes with linear, branched or ring structures might be formed.
The polycondensation of lactic acid is a step-growth reaction that results in carboxylic acid and alcoholic end-groups (di-end-functional polymers). Without further modification of the end-groups, the use of PLA oligomers as building blocks is therefore limited. For example telechelic PLA-diol receives a growing interest for the production of copolymers (amongst other with polyethylene glycol or with diisocyanate to form polyurethanes) cannot be produced directly by polycondensation.
The present invention aims to overcome the problems of the art be providing a new technique for producing well-defined functional lactic acid oligomers from lactide.